The invention relates to extracorporeal blood circuits for oxygenation and circulation of a patient""s blood during cardiac bypass surgery, and in particular to a self-contained pack assembly that includes the tubing and other disposable components of an extracorporeal blood circuit
During cardiac bypass surgery a patient""s heart is slowed or stopped for surgical repair, and his or her blood must be artificially oxygenated and pumped through the body using an extracorporeal support circuit. Using this system, venous blood is diverted from entering the right chambers of the heart and is instead directed through a series of tubes, pumps and filters, which provide fresh oxygen to the blood and return it to the body""s systemic circulation at the aorta. The oxygenated blood is then circulated throughout the body. The circuit thus ensures that the patient continues to be nourished by oxygenated blood flow while the heart is unable to function.
In performing such a procedure, a complicated apparatus is required. One or two blood reservoirs, an oxygenator (possibly combined with a heat exchanger), a blood pump, and multiple tubes to connect the various components are needed and must be assembled and arranged before surgery may begin. Typically a significant amount of time must be spent just prior to surgery to accomplish the set-up, and great attention must be paid to the details of this complicated task.
In a conventional extracorporeal support circuit, a venous line drains blood from the right side of the patient""s heart and delivers it to a blood reservoir. The blood is then pumped by a specially designed pump from the outlet of the blood reservoir into a blood oxygenator for oxygenation and cooling. The oxygenated blood is artificially pumped via an arterial line to the venous line, and the circuit is continued in this fashion until the surgical repair is complete.
The support circuit normally includes a blood scavenging sub-circuit for recovering and recycling blood from the surgical field. The sub-circuit includes one or more suckers (typically two to four) for sucking blood from the surgical field. Vacuum is applied to the suckers by a peristaltic positive displacement pump (also known as a roller pump) or wall vacuum to deliver the scavenged blood to a cardiotomy reservoir. The reservoir includes a defoaming section to remove entrained air and a filter. The outlet for the cardiotomy reservoir delivers the de-foamed, filtered blood to the venous reservoir of the main circuit. Various cardiotomy reservoirs are described in U.S. Pat. Nos. 3,891,416; 3,993,461; 4,208,193 and 4,243,531. The cardiotomy reservoir may alternatively be an integral portion of the venous blood reservoir in which the scavenged blood flows through a filter section and the venous blood does not.
A schematic diagram of a conventional extracorporeal support system is shown in FIG. 1. A reservoir 20 is provided for cleaning, debubbling, and collecting the blood. A tubing assembling called a pump loop 22 includes a pump inlet line 24 and a pump outlet line 26. These two lines are connected to an arterial pump 28, which for the purposes of this invention will most conveniently be of the type which has a pump header 30 which is separable from the motor portion. The pump outlet 26 leads to the inlet of the oxygenator 32, which may include a heat exchanger 34.
The elements so far described are connected to the body of the patient by a tubing assembly called an A-V loop 36. The A-V loop 36 includes a venous line 38 to carry the patient""s low-pressure, oxygen depleted venous blood to the reservoir, and an arterial line 40 carrying high-pressure, oxygen rich arterial blood from the oxygenator 32 back to the patient. It may be convenient to monitor the condition of the blood in these two lines, so a blood parameter monitor 42 may be provided having sensors 44 and 46, which are kept in chemical equilibrium with the blood flowing in the venous line 38 and the arterial line 40, respectively. A hematocrit monitor 48 may also be provided, having its own sensor 50, conveniently monitoring the blood in the venous line 38.
It may be convenient to perfuse the patient""s heart directly with a different solution than is provided to the rest of the patient""s body. Cardioplegia solution is typically used in this fashion to slow or stop the patient""s heart during surgery. A cardioplegia pump 52 may be used to deliver cardioplegia solution supplied by solution line 56 from a solution supply 58. The cardioplegia pump outlet line 60 passes through a cardioplegia heat exchanger 62 and a bubble trap 64 before delivering cardioplegia solution to the heart at the cardioplegia catheter 66.
Two suction lines are typically provided to recapture blood from the site of the surgical incision that has escaped the closed system. The first is called the vent line 68, and runs from a vent catheter 70 through a vent pump 72 to the reservoir 20. The second is called the suction line 74, and runs from a suction device 76 through a suction pump 78 and once again to the reservoir 20.
To prepare the system for use, each of the tubing connections must be individually made by a skilled person in the operating room. Many of these connections are between disposable system components, Such as tubes and filters, which could advantageously be pre-connected and assembled in an assembly pack for quick attachment to the nondisposable elements of the system, thus enhancing operating room efficiency. However, no such assembly packs have heretofore been developed in the art.
The invention provides an assembly pack that contains the major disposable components of an extracorporeal support circuit, conveniently packaged in ready-to-use condition. All the tubing needed to connect the patient for bypass surgery is included in the pack, with the necessary attachments between the various elements in the pack pre-made in a sterilized condition. In preparation for surgery, only a few connections must be made between the assembly pack and the nondisposable elements of the circuit compared to the numerous connections that were previously required. The assembly pack allows one to carry and mount all the disposable paraphernalia needed for perfusion with a single hand
The pack assembly is built around a backbone called the carrier, which serves as a support and handle for the other components. Preferably, a reservoir and an oxygenator are both physically but releasably attached to this carrier. Disposed around these central components, and attached to them in some way, will preferably be at least one tray. In preferred embodiments, two trays will be present, and it is considered particularly convenient that each of these trays be releasably attached to both the carrier and the reservoir. The carrier preferably has a handle so that the pack assembly can be easily moved and manipulated after being removed from its shipping container.
In preferred embodiments, various tubing assemblies will be pre-attached to the reservoir and the oxygenator, with the majority of their lengths conveniently coiled and disposed within the trays. Most conveniently, the trays will themselves be divided into several compartments, and tubes that share some functional relationship will be packaged together in the same compartment, separated from other tubes with different functions.
In particular, in one preferred embodiment there is a prime line for priming the reservoir prior to surgery. This prime line conveniently has a priming tube attached to the reservoir at one end and a bag spike at the other end. The end with the bag spike is disposed within a first compartment in one of the trays. It is particularly convenient if that tray has a narrow cut-out portion to admit the free end of the prime line so that the prime line may be deployed and attached to a bag of saline solution without first detaching the tray. In some embodiments, it is convenient that one or more of the tubes will have a grommet, and that grommet will allow the tube to pass through the cut-out portion in the wall of the tray while maintaining a sterile seal.
In similar fashion, an A-V loop, a pump loop, and one or more suction lines will be present in a preferred embodiment, and each group of lines will be packaged with most of their lengths within their own individual compartment within one of the trays. In the most preferred embodiments cut-outs are provided within the side walls of the trays so that each line or group of lines may be deployed before the trays are detached and discarded.
In the most preferred embodiment the trays hang vertically in the pack assembly, and a cover sheet is provided for each tray in order to keep the components within it enclosed. Any moderately sturdy sheet material should be suitable for the purpose, but a film of transparent polymeric material is considered particularly preferred so that the components within the trays can be inspected visually after assembly.
In a preferred embodiment of the invention, the pack assembly will include a barrier pouch enclosing all of its components. In the most preferred embodiment, the pack assembly is xe2x80x9cself-contained,xe2x80x9d meaning that all the tubing and disposable elements necessary to connect a patient for bypass surgery is included in the pack.